The present invention relates to a device for a heat-emitting unit for connection to an electric voltage source. In this type of unit a thermostat device can be used to maintain a certain predetermined temperature. When this has been reached, the temperature in the unit will oscillate about the predetermined set temperature, the thermostat alternating between on and off position. If a graph is plotted for the temperature in relation to the time after the temperature in the unit has reached the value set, it is found that a curve is obtained having the nature of a sine wave. The positive parts of the curve represent the time periods when the thermostat is disconnected and the negative parts of the curve represent the time periods when the thermostat is switched on. It might also be said that, after reaching the set temperature, a number of positive and negative amplitudes follow, having certain duration. The duration of the amplitudes is dependent on the surrounding temperature prevailing around the heat-emitting unit. Under certain circumstances the continuance of alternating temperature amplitudes after the set temperature has been reached for an indefinite period, i.e. as long as the heat-emitting unit is connected to an electric voltage source, may be a drawback.
Heat-emitting units are widely used for seats in transport means such as cars, aircraft, boats or the like. Heat-emitting units may be placed both in the seat and in the backrest and may consist of several units, generally connected in series with each other. The units may either be in the form of pads to be placed on top of existing seats, or they may be built-in to both seat and backrest. For reasons of health, heat-emitting units are necessary in transport means since a cold seat may cause illness in the person using it. This is the reason for using heat-emitting units provided with thermostat devices. The temperature is set at, say, 37.degree. C. and the seat and backrest are quickly heated. Once the desired temperature has been reached, the temperature will oscillate about the value set and it has been found that, after a certain time, the human body finds the set value to be unpleasantly high and it must therefore be reduced to about 32.degree. C., a temperature experienced as pleasant. At a pleasant temperature the human body also emits a certain amount of heat which is generally sufficient to keep the seat and backrest at a temperature experienced as pleasant. There is thus also another alternative to altering the heat in the seat, and that is to cut the voltage supply to the heat-emitting unit or units in the seat, after a certain period at full heat.